Lawyers for WikiLeaks founder Julian Assange may launch a new appeal against his European arrest warrant after e-mails between Swedish prosecutors and the UK appeared to show British authorities deliberately resisted making progress in his case.

Assange’s legal team say the messages between the Crown Prosecution Authority (CPS) and Swedish prosecutor, which were revealed by Italian newspaper L’Espresso on Monday, show the parties were “more interested in winning the case [against him] than finding the truth.”

Speaking to the Guardian on Monday, Assange called the revelations “astonishing.”

“I have been on the phone with my lawyers all morning and they are as shocked as I am,” he said.

Assange has been in the Ecuadorian Embassy for three years after claiming asylum to avoid extradition to Sweden to answer four sex offense allegations, three of which have since been dropped. Assange has always denied the allegations.

The Australian says he wishes to avoid further extradition to the US, where he would be tried for espionage and has repeatedly requested that Swedish prosecutors interview him inside the London embassy.

The e-mails were accessed by L’Espresso through Freedom of Information (FoI) requests to the Swedish and British governments.

In one message, dating from January 2011, Paul Close, a CPS special crime division lawyer, warned the Swedes that “even if the defendant was to consent to such an interview (by appointment) on a mutually agreed basis, the [defence] would without any doubt seek to turn the event to its advantage.”

“It would inevitably allege it was conclusive proof that the Swedish authorities had no case whatsoever against him [Assange] and hence the interview was in the hope that he would make a full and frank confession.”

“He would of course have no obligation (under English law) to answer any questions put to him,” Close added.

Another said it would “not be prudent" for Swedish lawyers to interview Assange in the Ecuadorian embassy.